Calcite, which gets its name from "chalix" the Greek word for lime .Calcite is a common constituent of limestone in particular, much of which is formed from the shells of dead marine organisms. CALCITE is a carbonate of lime (CaCo3). Calcite is the primary mineral in metamorphic marble .It has a Mohs hardness of 3, a specific gravity of 2.71, and its luster is vitreous in crystallized varieties. Color is white or none, though shades of gray, red, yellow, green, blue, violet, brown, or even black can occur when the mineral is charged with impurities. Calcite is transparent to opaque and has the ordinary refractive index varies roughly between 1.6 and 1.4, while the extraordinary refractive index varies between 1.9 and 1.5.